1. Technical Field
This invention relates to a rotary electric machine for a vehicle such as a passenger car and a truck.
2. Related Art
A known power generator for a vehicle, as disclosed in Japanese Patent Application Publication No. 2010-110176, includes a power conversion device that is adapted to rectify an output voltage of an armature winding via a power converting section composed of a plurality of switching elements. In the disclosed power conversion device, it is diagnosed whether or not an upper arm switching element is on, for example, by checking (i) that its parasitic diode is in an on-state, (ii) that a gate command for the upper-arm switching element is ON, and (iii) that a phase voltage is within a predetermined range (equal to or lower than a threshold V4).
In the disclosed power conversion device, however, there is a disadvantage that although it can be determined whether or not each switching element is normally on just during an energization period of its parasitic diode, it cannot be reliably determined whether or not there has occurred an abnormality prior to start of the synchronous rectification, in particular, whether or not each switching element is short-circuited prior to start of the synchronous rectification.
Japanese Patent Application Publication No. 2010-110176 describes how to diagnose operation of each switching element after the synchronous rectification is started, but it is silent about a start condition for starting or restarting the synchronous rectification immediately after engine start or after suspension of the synchronous rectification from any cause. Inadvertent start of the synchronous rectification at timing when a phase voltage waveform is disturbed or when the switching element is short-circuited may lead to a short-circuit fault between terminals of a vehicle battery through the upper-arm and/or lower-arm circuit sections. Therefore, it is desirable to start the synchronous rectification after having ensured that such a short-circuit fault may not occur. In the absence of at least a short-circuit fault in the switching elements, the diode rectification can be performed even in the presence of an open fault, which enables power generation to be continued.
In consideration of the foregoing, exemplary embodiments of the present invention are directed to providing a rotary electric machine for a vehicle that is capable of starting synchronous rectification through switching elements after having ensured absence of a short circuit fault.